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| United States Patent |
5,727,993
|
|
Kodate
|
March 17, 1998
|
Plastic flexible grinding stone
Abstract
The plastic flexible grinding stone according to the present invention
comprises a plastic flexible material having mixed therewith a powder
synthetic detergent and an abrasive such as silica sand and calcium
carbonate composed of grains from 3 to 50 .mu.m in diameter, and is
capable of removing simultaneously minute protrusions and stain from
coated surfaces such as of rolling stocks.
| Inventors:
|
Kodate; Tadao (Ohmiya, JP)
|
| Assignee:
|
Joybond Co., Inc. (Katsushika-ku, JP)
|
| Appl. No.:
|
555763 |
| Filed:
|
November 9, 1995 |
Foreign Application Priority Data
| Current U.S. Class: |
451/59; 451/103; 451/526 |
| Intern'l Class: |
B24B 007/00 |
| Field of Search: |
451/103,104,113,526,523,540
|
References Cited
U.S. Patent Documents
| 4150955 | Apr., 1979 | Samuelson.
| |
| 4264337 | Apr., 1981 | Fenster et al.
| |
| 4421526 | Dec., 1983 | Strickman et al.
| |
| 4512859 | Apr., 1985 | Inoue.
| |
| 5125191 | Jun., 1992 | Rhoades.
| |
| 5152809 | Oct., 1992 | Mattesky.
| |
| 5203883 | Apr., 1993 | Perry.
| |
| Foreign Patent Documents |
| 0 196 832 | Oct., 1986 | EP.
| |
| 1-97572 | Apr., 1989 | JP.
| |
| 4-11335 | Feb., 1992 | JP.
| |
| 92/00153 | Jan., 1992 | WO.
| |
Other References
English translation of Japanese Patent Application 4-11335 (Feb. 28, 1992).
English translation of Japanese patent Application 1-97572 (Apr. 17, 1989).
Cryovac, "MPD 2055 Film," 2 pages (publication date is unknown but it is at
least as early as Oct. 1995).
|
Primary Examiner: Rose; Robert A.
Attorney, Agent or Firm: Conley, Rose & Tayon, P.C.
Parent Case Text
This is a continuation of application Ser. No. 08/102,972 filed Jul. 28,
1993 now U.S. Pat. No. 5,476,416.
Claims
What is claimed is:
1. A plastic flexible tool adapted to remove a protrusion or stain from a
surface, comprising:
a plastic flexible material having mixed therewith an abrasive comprising
grains from about 3 to 50 .mu.m in diameter, and wherein the tool
distributes polishing force per area during use such that, when the tool
is applied with polishing force per area to a surface with a protrusion or
stain during use, polishing force per area applied to the surface is less
than the polishing force per area applied to the protrusion or stain.
2. The plastic flexible tool of claim 1 wherein the plastic flexible tool
comprises a substantially flat surface.
3. The plastic flexible tool of claim 1 wherein the tool is adapted to
remove a protrusion or stain from a coated surface without substantially
scratching the coated surface.
4. The plastic flexible tool of claim 1 wherein the abrasive comprises
grains from about 20 to 30 .mu.m in diameter.
5. The plastic flexible tool of claim 1 wherein the tool comprises 60 to 80
parts by weight with respect to 100 parts per weight of the flexible
material.
6. The plastic flexible tool of claim 1 wherein the abrasive comprises
silica sand.
7. The plastic flexible tool of claim 1 wherein the abrasive comprises
calcium carbonate.
8. The plastic flexible tool of claim 1 wherein the abrasive comprises
alumina.
9. The plastic flexible tool of claim 1 wherein the abrasive comprises a
ceramic material.
10. The plastic flexible tool of claim 1 wherein the abrasive comprises
Green Carborundum.
11. The plastic flexible tool of claim 1 wherein the tool is substantially
incompressible.
12. The plastic flexible tool of claim 1 wherein the abrasive is
substantially buried within the tool.
13. The plastic flexible tool of claim 1 wherein the abrasive is
substantially buried within the tool such that when the tool is pressed
against a surface the abrasive within the tool does not substantially
protrude from the tool.
14. The plastic flexible tool of claim 1 wherein the tool is adapted such
that, when the tool is applied with polishing force to a surface, a
protrusion on the surface is substantially removed during use as a result
of collisions occurring inside the tool between the abrasive and the
protrusion.
15. The plastic flexible tool of claim 1 wherein the tool is adapted such
that, when applied with polishing force to a coated surface during use, a
protusion on the coated surface is substantially removed during use
without substantially scratching the coating of the surface.
16. The plastic flexible tool of claim 2 wherein the abrasive is
substantially buried inside the plastic flexible tool such that the
abrasive does not substantially protrude from the substantially flat
surface of the tool.
17. The plastic flexible tool of claim 1 wherein the tool is adapted such
that, when the tool is applied with polishing force to a surface with a
protrusion during use, polishing force applied to the surface is about
1/30 to 1/200 of polishing force applied to the protrusion, and wherein
the protrusion is substantially removed from the surface without
substantially scratching the surface.
18. The plastic flexible tool of claim 1 wherein the tool is adapted such
that, when the tool is applied with polishing force to a surface with a
protrusion during use, polishing force applied to the surface is about
1/80 to 1/100 of polishing force applied to the protrusion.
19. The plastic flexible tool of claim 1 wherein the tool is adapted such
that, when the tool is applied with polishing force to a surface with a
protrusion during use, polishing force applied to the surface is about 0.5
to 3.0 percent of polishing force applied to the protrusion.
20. The plastic flexible tool of claim 1 wherein the grains have a diameter
in the range of between about 20 to 30 .mu.m.
21. The plastic flexible tool of claim 1 wherein the tool comprises a
mixture of at least two abrasives from the group consisting of silica
sand, calcium carbonate, alumina, ceramics, and Green Carborundum.
22. The plastic flexible tool of claim 1 wherein the tool comprises a
substantially flat surface, and wherein the abrasive is substantially
buried inside the tool such that abrasive does not substantially protrude
from the substantially flat surface of the tool.
23. The plastic flexible tool of claim 1 wherein the plastic flexible tool
is adapted, when applied with polishing force to a surface during use, to
remove a protrusion or stain from the surface without substantially
scratching the surface.
24. The plastic flexible tool of claim 1, wherein the plastic flexible
material and abrasive are present in a substantially homogeneously mixed
state.
25. The plastic flexible tool of claim 1, further comprising a powder
synthetic detergent.
26. The plastic flexible tool of claim 1, further comprising a powder
synthetic detergent comprising grains from 30 to 1,500 .mu.m in diameter.
27. The plastic flexible tool of claim 25 wherein the powder synthetic
detergent is added at an amount of from 0.5 to 20 parts by weight with
respect to 100 parts by weight of the flexible material.
28. The plastic flexible tool of claim 25 wherein the powder synthetic
detergent comprises grains from 30 to 1,500 .mu.m in diameter and is added
at an amount of from 0.5 to 20 parts by weight with respect to 100 parts
by weight of the flexible material.
29. A method of polishing a protrusion or stain from a surface, comprising:
applying a plastic flexible tool to the surface, the plastic flexible tool
comprising a plastic flexible material having mixed therewith an abrasive
comprising grains from about 3 to 50 .mu.m in diameter; and
applying a force to the plastic flexible tool such that a polishing force
per area is applied by the plastic flexible tool to a protrusion on the
surface, and such that the amount of force per area applied to the surface
is about 1/30 to 1/200 of the amount of force per area applied to the
protrusion.
30. The method of claim 29, further comprising pressing the plastic
flexible tool against the surface, thereby deforming the plastic flexible
tool to form a substantially flat surface on the plastic flexible tool.
31. The method of claim 29 wherein the tool is pressed against the surface
such that the protrusion substantially embeds itself into the
substantially flat surface of the tool.
32. The method of claim 29 wherein the tool is pressed against the surface
such that the protrusion substantially embeds itself into the
substantially flat surface of the tool, and further comprising
reciprocating the substantially flat surface of the plastic flexible tool
on the surface such that the protrusion protrudes into the tool and is
brought into contact with abrasive inside the tool.
33. The method of claim 29, further comprising reciprocating the
substantially flat surface of the plastic flexible tool on the surface.
34. The method of claim 29 wherein the abrasive is substantially buried
inside the plastic flexible tool such that the abrasive does not
substantially protrude from the substantially flat surface of the tool.
35. The method of claim 30 wherein the abrasive is substantially buried
inside the plastic flexible tool such that the abrasive does not
substantially protrude from the substantially flat surface of the tool,
and wherein the tool is pressed against the surface such that a protrusion
substantially embeds itself into the substantially flat surface of the
tool, and further comprising reciprocating the substantially flat surface
of the plastic flexible tool on the surface such that the protrusion
protrudes into the tool and is forcefully contacted with abrasive inside
the tool.
36. The method of claim 35 wherein the surface is not forcefully contacted
with abrasive.
37. The plastic flexible tool of claim 1 wherein the abrasive is located
flush with an outer surface of the flexible tool.
38. The method of claim 35 wherein force is applied to the protrusion and
the surface, and wherein the amount of force applied to the protrusion is
about 1/80 to 1/100 of the amount of force applied to the surface.
39. The method of claim 35 wherein a force is applied to the protrusion,
and wherein about 0.5 to 3.0 percent of such force is substantially
simultaneously applied to the surface.
40. The method of claim 29, further comprising adding water to the surface.
41. The method of claim 29, further comprising removing the stain or
protrusion from the surface without substantially scratching the surface.
42. The plastic flexible tool of claim 1 wherein the abrasive is located
flush with an outer surface of the flexible tool, and wherein the abrasive
slips within the outer surface of the tool upon detecting resistance from
the surface.
43. A method of polishing a protrusion or stain from a coated surface,
comprising:
applying a plastic flexible tool to the coated surface, the plastic
flexible tool comprising a plastic flexible material having mixed
therewith an abrasive comprising grains from about 3 to 50 .mu.m in
diameter;
pressing the plastic flexible tool against the coated surface to form a
substantially planer surface on the plastic flexible tool; and
reciprocating the substantially planar surface of the plastic flexible tool
with polishing force on the coated surface for less than about 30 seconds,
thereby applying a polishing force per area to the coated surface and to
the protrusion or stain on the coated surface, the polishing force per
area applied to the coated surface being less than the polishing force per
area applied to the protrusion or stain.
44. The method of claim 43 wherein the plastic flexible tool has a shape
which is transformable by pressure but incapable of recovering its initial
form upon release of pressure.
45. The method of claim 43 wherein the abrasive comprises grains from about
20 to 30 .mu.m in diameter.
46. The method of claim 43 wherein the plastic flexible tool comprises 60
to 80 parts by weight of abrasive with respect to 100 parts by weight of
flexible material.
47. The method of claim 43 wherein the abrasive is flush with an outer
surface of the flexible material, and wherein the abrasive slips within
the flexible material upon detecting a resistance from the surface.
48. The method of claim 43 wherein the abrasive is flush with an outer
surface of the flexible material, and wherein the abrasive slips within
the flexible material upon detecting a resistance from the surface such
that the force applied to the surface is lessened by slipping of the
abrasive.
49. The method of claim 43 wherein the protrusion or stain is substantially
removed in less than about 30 seconds.
50. The method of claim 43 wherein the protrusion is removed in a time at
least about as great as the time in which the stain is removed.
51. The method of claim 43 wherein the flexible tool comprises a mixture of
at least two abrasives from the group consisting of silica sand, calcium
carbonate, alumina, ceramics, and Green Carborundum.
52. The method of claim 43 wherein the flexible material is substantially
uniformly applied to the surface.
53. The method of claim 43 wherein the flexible material is applied to a
curved surface, and the flexible material substantially conforms to the
curved surface.
54. The method of claim 43 wherein the abrasive is flush with an outer
surface of the flexible material, and wherein the abrasive slips within
the flexible material upon detecting a resistance from the surface, and
wherein the protrusion or stain is removed from the surface as a result of
contact between the abrasive and the protrusion or stain, and wherein the
slipping of the abrasive within the flexible material inhibits scratching
of the surface by the abrasive.
55. The method of claim 43 wherein the amount of force per area applied to
the surface is about 1/30 to 1/200 of the amount of force per area applied
to the protrusion.
56. The method of claim 43 wherein the amount of force per area applied to
the surface is less than 3/100 of the amount of force per area applied to
the protrusion.
57. A method of polishing a protrusion or stain from a surface, comprising:
applying a plastic flexible tool to the surface, the plastic flexible tool
comprising a plastic flexible material having mixed therewith an abrasive
comprising grains from about 3 to 50 .mu.m in diameter; and
applying a force to the plastic flexible tool such that a polishing force
per area is applied by the plastic flexible tool to a protrusion or stain
on the surface, and such that the amount of force per area applied to the
surface is less than the amount of force per area applied to the
protrusion or stain.
58. The method of claim 57, further comprising pressing the plastic
flexible tool against the coated surface to form a substantially flat
surface on the plastic flexible tool.
59. The method of claim 57, further comprising reciprocating the
substantially planar surface of the plastic flexible tool with polishing
force on the coated surface for less than about 30 seconds, thereby
applying the polishing force per area to the coated surface and to the
protrusion or stain on the coated surface.
60. The method of claim 57 wherein the surface is coated, and wherein the
protrusion or stain is removed from the coated surface without
substantially scratching the coated surface.
61. The method of claim 57 wherein the tool is pressed against the surface
such that the protrusion substantially embeds itself into the
substantially flat surface of the tool.
62. The method of claim 57 wherein the tool is pressed against the surface
such that the protrusion substantially embeds itself into the
substantially flat surface of the tool, and further comprising
reciprocating the substantially flat surface of the plastic flexible tool
on the surface such that the protrusion protrudes into the tool and is
brought into contact with abrasive inside the tool.
63. The method of claim 57 wherein the amount of force per area applied to
the surface is about 1/30 to 1/200 of the amount of force per area applied
to the protrusion or stain.
64. The method of claim 57 wherein the amount of force per area applied to
the surface is less than about 3/100 of the amount of force per area
applied to the protrusion or stain.
65. The method of claim 57 wherein the abrasive comprises grains from about
20 to 30 .mu.m in diameter.
66. The method of claim 57 wherein the tool comprises 60 to 80 parts by
weight with respect to 100 parts per weight of the flexible material.
67. The method of claim 57 wherein the abrasive is substantially buried
inside the plastic flexible tool such that the abrasive does not
substantially protrude from the substantially flat surface of the tool.
68. The method of claim 58 wherein the abrasive is substantially buried
inside the plastic flexible tool such that the abrasive does not
substantially protrude from the substantially flat surface of the tool,
and wherein the tool is pressed against the surface such that a protrusion
substantially embeds itself into the substantially flat surface of the
tool, and further comprising reciprocating the substantially flat surface
of the plastic flexible tool on the surface such that the protrusion
protrudes into the tool and is forcefully contacted with abrasive inside
the tool.
69. The method of claim 57 wherein the surface is coated, and wherein the
coated surface is not forcefully contacted with abrasive.
70. The method of claim 68 wherein force is applied to the protrusion and
the surface, and wherein the amount of force applied to the protrusion is
about 1/30 to 1/200 of the amount of force applied to the surface.
71. The method of claim 68 wherein force is applied to the protrusion and
the surface, and wherein the amount of force applied to the protrusion is
about 1/80 to 1/100 of the amount of force applied to the surface.
72. The method of claim 68 wherein a force is applied to the protrusion,
and wherein about 0.5 to 3.0 percent of such force is substantially
simultaneously applied to the surface.
73. The method of claim 43, further comprising adding water to the surface.
74. The method of claim 57, further comprising adding water to the surface.
75. The method of claim 57, further comprising removing the stain or
protrusion from the surface without substantially scratching the surface.
76. The method of claim 57 wherein the flexible tool comprises a mixture of
at least two abrasives from the group consisting of silica sand, calcium
carbonate, alumina, ceramics, and Green Carborundum.
77. The method of claim 57 wherein the flexible material is substantially
uniformly applied to the surface.
78. The method of claim 57 wherein the flexible material is applied to a
curved surface, and the flexible material substantially conforms to the
curved surface.
79. The plastic flexible tool of claim 1 wherein the tool is adapted to
remove the stain and the protrusion in less than about 30 seconds during
use.
80. The plastic flexible tool of claim 1 wherein the tool is adapted to
remove the stain and the protrusion in less than about 21 seconds during
use.
81. The plastic flexible tool of claim 1 wherein the tool is adapted to
remove the stain in at least the amount of time required for the removal
of the protrusion.
82. The plastic flexible tool of claim 1 wherein the abrasive extends from
an outer surface of the flexible tool, and wherein the tool is adapted
such that abrasive slips within the outer surface of the tool upon
detecting resistance from the surface such that the polishing force per
area applied to the surface is lessened by the slipping of the abrasive
during use.
83. The plastic flexible tool of claim 1 wherein the abrasive is located
flush with an outer surface of the flexible tool, and wherein the tool is
adapted such that abrasive slips within the outer surface of the tool upon
detecting resistance from the surface such that the polishing force per
area applied to the surface is lessened by the slipping of the abrasive
during use.
84. The plastic flexible tool of claim 1 wherein the tool is adapted such
that it substantially conforms to the shape of the shape of a curved plane
on the surface during use.
85. The plastic flexible tool of claim 1 wherein the abrasive extends from
an outer surface of the flexible material, and wherein the tool is adapted
such that the abrasive slips within the flexible material upon detecting a
resistance from the surface, and wherein the stain is removed from the
surface as a result of contact between the abrasive and the stain, and
wherein the slipping of the abrasive within the flexible material inhibits
scratching of the surface by the abrasive during use.
86. The plastic flexible tool of claim 1 wherein the abrasive is flush with
an outer surface of the flexible material, and wherein the tool is adapted
such that the abrasive slips within the flexible material upon detecting a
resistance from the surface, and wherein the stain is removed from the
surface as a result of contact between the abrasive and the stain, and
wherein the slipping of the abrasive within the flexible material inhibits
scratching of the surface by the abrasive during use.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plastic flexible grinding stone for use
in removing, by polishing, small protrusions which generate on a coated
surface of rolling stocks and industrial machines, as well as in removing
stain and oil films from the surface of window glasses.
2. Prior Art
When rolling stocks are placed in parking lots near to railways and iron
works, or in places close to construction sites where a coating operation
is conducted, iron powder and paint mist fly onto the coated surface of
the rolling stocks and adhere thereto to form minute protrusions. Such
unfavorable protrusions were conventionally removed by polishing the
surface using a compound or a sandpaper.
However, when a compound or a sandpaper is applied to the surface to remove
the protrusions, not only the protrusions but also the coated surface are
brought into contact with the abrasive to form scratches or flaws on the
coated surface. As illustrated schematically in FIG. 3(a), it can be seen
that this type of polishing suffers very poor operability, because the
abrasive force is fully (100%) exerted on the coated surface if the
abrasive force is fully applied to the protrusions.
With a view to ameliorate the poor operability of the conventional method,
the present to inventors has have previously proposed in JP-B-4-11335 (the
term "JP-B-" as referred to herein signifies "an examined published
Japanese patent application"), a plastic flexible grinding stone
comprising a plastic flexible material having mixed therewith fine
abrasive such as silica sand and calcium carbonate. When polishing is
conducted using the proposed grinding stone, however, as shown in FIG.
3(b) no (0%) polishing force is exerted on the coated surface when the
polishing force is fully(100%) applied to the protrusions. Accordingly, it
can be seen that a favorable operability is realized for the protrusions,
but that the stain cannot be removed from the coated surface.
Conventional grinding stones include plastic flexible ones comprising a
plastic flexible material having incorporated therein silica sand and
calcium carbonate. The protrusions having formed by adhesion of minute
granules or droplets to the coated surface can be removed completely using
those grinding stones, however, the stain was left for another means for
its removal.
SUMMARY OF THE INVENTION
An object of the present invention is to obtain a smooth and plain coated
surface by polishing, and yet removing stain from the smooth and plain
surface. Accordingly, the present invention comprises controlling both the
polishing force being exerted to the protrusions and the polishing force
being applied to the planar surface.
The object of the present invention can be accomplished by a plastic
(transformable by pressure but incapable of recovering its initial form
upon release of pressure) flexible grinding stone comprising a plastic
flexible material having mixed therewith a powder of a synthetic detergent
and at least one type of fine abrasive composed of grains from 3 to 50
.mu.m in diameter and selected from the group consisting of silica sand,
calcium carbonate, alumina, ceramics, and Green Carborundum (silicon
carbide abrasive).
The powder of the synthetic detergent is composed of grains from 30 to
1,500 .mu.m in diameter. The powder of the synthetic detergent is mixed at
an amount of from 0.5 to 20 parts by weight with respect to 100 parts by
weight of the flexible material. The size of the grains of the synthetic
detergent is confined to the range above, because grains too large in size
cause the grains to protrude from the polishing surface, whereas grains
too small in size make it difficult to achieve a homogeneously mixed state
in the flexible material. The amount of the synthetic detergent is limited
to the range above. If the amount is too small, the stain is
insufficiently removed from the surface; if the amount is too large, on
the other hand, fine abrasive tends to appear excessively on the surface
so as to impair the polished surface.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an explanatory figure showing a plastic flexible grinding stone
according to the present invention in use;
FIG. 2 is a cross sectional view of a plastic flexible grinding stone with
the abrasive thereof forming protrusions against the polishing surface;
and
FIG. 3 is a schematic figure provided as an explanatory means to show the
exertion of polishing force against the protrusions and stain.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is illustrated in greater detail referring to a
non-limiting example below. It should be understood, however, that the
present invention is not to be construed as being limited thereto.
EXAMPLE
A plastic flexible grinding stone was produced by mixing 100 parts by
weight of a petroleum resin (polybutene in the present example) as a
plastic flexible material with 65 parts by weight of fine silica sand and
calcium carbonate grains from 20 to 30 .mu.m in diameter, and 5 parts by
weight of a powder synthetic detergent composed of grains 500 .mu.m in
diameter. The powder synthetic detergent may be a soap of any type having
a cleaning power.
Referring to FIG. 1, the flexible grinding stone 1 above was used for
removing a small protrusion 2 (0.5 mm in height and 1 mm in width) from
the coated surface. The flexible grinding stone was pressed against a
planar coated surface A to form a flat plane on the flexible grinding
stone. Fine abrasive 3 and powder synthetic detergent 4 are distributed
within a flexible material 5 as shown in FIG. 2. By reciprocating the
planar surface of the flexible grinding stone 1 on the coated surface
having the protrusion 2 thereon, the small protrusion 2 was removed
completely from the coated surface in about 30 seconds. The stain on the
coated surface was removed at the same time. A coated surface as plain and
smooth as the surface before polishing was obtained free from scratches
and flaws by the polishing operation.
Referring again to FIG. 2, a pore 4a can be seen to open on the surface in
contact with the coated planar surface A, due to the dissolution of the
powder synthetic detergent 4. The open pore 4a facilitates the fine
abrasive to stick against the polishing surface. In this manner, the
polishing speed of the plain surface is accelerated.
Hard fine grains such as of alumina, ceramics, and Green Carborundum may be
incorporated in the flexible material as the fine abrasive 3 in the place
of the aforementioned grains of silica sand and calcium carbonate. Those
fine grains may be used either alone or as a mixture of two or more
selected therefrom. The fine abrasive grains in the example were confined
to a diameter in the range of 20 to 30 .mu.m, but the size may be freely
selected within a range of from 3 to 50 .mu.m depending on the object of
polishing. The amount of the fine abrasive such as the fine grains of
silica sand and calcium carbonate may be varied within a range of from 60
to 80 parts by weight with respect to 100 parts weight of the flexible
material.
In removing small protrusions from the coated surface using the plastic
flexible grinding stone according to the present invention, the flexible
grinding stone is pressed against a flat and hard plane to form a flat
surface on the grinding stone. At this stage, the fine abrasive is buried
inside the flat surface of the grinding stone to leave no edges thereof
sticking out from the flat surface of the flexible grinding stone.
When the flat surface of the flexible grinding stone is placed over the
small protrusion on the coated surface, the small protrusion bores a small
hole on the flat surface of the flexible grinding stone and accommodates
itself therein. This stage is illustrated in FIG. 1. When the flexible
grinding stone is repeatedly reciprocated on the coated surface along the
direction indicated with the arrows shown in FIG. 1, the flat surface of
the flexible grinding stone moves with its surface being cut with the
small protrusion. Since the fine abrasive is not pressed uniformly by the
small protrusion in this stage, the edges of the fine abrasive stick out
from the flexible material.
Accordingly, the fine abrasive sticking out from the flexible material is
brought forcibly into contact with the small protrusion to conduct
polishing. The flat surface having formed on the flexible grinding stone
is also brought into contact with the coated surface in this case,
however, the coated surface suffers no scratches or flaws because the
edges of the fine abrasive do not stick out from the flat surface of the
flexible material.
Water may be sprayed to the region on which the flexible grinding stone is
moved or to the flexible grinding stone. By taking this means, the powder
detergent being incorporated into the flexible grinding stone dissolves
into the water to allow the fine abrasive to be exposed on the surface.
The amount of the exposed fine abrasive can be controlled by the amount of
the powder detergent being incorporated into the flexible grinding stone.
The fine abrasive grains sticking out from the polishing surface
immediately slip into the flexible material upon detection of a resistance
on the polishing surface. In this manner, the polishing force against a
flat surface is exerted at about 1/80 to 1/100 of the force applied to a
protrusion (in a case 5% by weight of a powder synthetic detergent is
added to the grinding stone). This signifies a pertinent force is applied
to both the protrusion and the surface stain in conducting polishing as
shown in FIG. 3(c); specifically, 0.5 to 3% of a polishing force is
applied to the stain with respect to 100% of the force applied to the
protrusion.
The polishing ability against a flat surface may be controlled in the range
of from 1/30 to 1/200 by varying the content of the powder synthetic
detergent depending on the object of polishing.
The polished state and the removal of the stain were evaluated while
changing the addition of the powder synthetic detergent 4 with respect to
100 parts by weight of the flexible material 5. The results are summarized
in Table 1. In the evaluation, the polishing speed signifies the time
consumed for removing a protrusion 0.5 mm in height and 1 mm in width, and
the speed for removing the stain refers to the time necessary for removing
the stain around the protrusion. The frictional force in this case was
evaluated from the degree of the force applied by the operator to the
grinding stone. A flexible grinding stone comprising 65 parts by weight of
fine abrasive grains 25 .mu.m in average diameter was used. A conventional
flexible grinding stone containing the same fine abrasive but no powder
synthetic detergent was also evaluated for comparison. The results are
summarized in Table 1.
TABLE 1
______________________________________
Content of
Speed of Speed of
Detergent
Polishing
Stain removal
Frictional
(pts. wt.)
(sec) (sec) Force Evaluation
______________________________________
0 30 Unable to remove
Large Poor
0.5 26 48 Medium Fair
3 25 38 Medium Fair
10 20 20 Small Good
20 19 20 Small Good
25 31 22 Small Poor to Fair
______________________________________
Table 1 shows that the stain can be rapidly removed by adding 0.5 parts by
weight or more of a powder synthetic detergent, but that the polishing
speed for a protrusion is lowered by adding the detergent in excess of 20
parts by weight. Furthermore, it can be seen that the polishing can be
conducted with a small frictional force by adding 0.5 parts by weight or
more of a powder synthetic detergent.
In removing both the protrusion and the stain from a coated surface, it is
preferred that the protrusion and the stain are removed within the same
duration of time, or the protrusion is removed faster than the stain. It
is not favorable that the stain be removed faster than the protrusion,
because the polishing marks of the protrusion may somewhat remain on the
coated surface. Accordingly, by using a flexible grinding stone having
added therein a powder synthetic detergent at an amount of from 0.5 to 20
parts by weight, the stain can be removed completely upon finishing the
removal of the protrusion to yield a favorable operability.
Furthermore, in the comparative example above, scratches were found to be
formed around the protrusion. However, the examples according to the
present invention suffered no scratches or flaws and yielded a flat and
smooth surface around the polished area because of the lubricity imparted
to the grinding stone.
Then, grinding stones containing powder synthetic detergent 4 with varying
grain diameter were produced to evaluate the polishing state and the
removal of the stain. The results are summarized in Table 2 below. The
evaluation was carried out in the same manner as in the previous
evaluation whose results are summarized in Table 1. A flexible grinding
stone comprising 65 parts by weight of fine abrasive grains 25 .mu.m in
average diameter was used, and the powder synthetic detergent was added at
an amount of 10 parts by weight.
TABLE 2
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Diameter of
Speed of Speed of
Detergent
Polishing Stain removal
Frictional
(.mu.m) (sec) (sec) Force Evaluation
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15 28 40 Medium Poor to Fair
30 24 32 Medium Fair
100 20 28 Small Good
500 20 26 Small Good
1000 23 23 Small Good
1500 24 25 Small Good
2000 30 25 Small Poor to Fair
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Table 2 shows that the polishing of the small protrusions and the removal
of stain take a longer time when a grinding stone containing powder
synthetic detergent 30 .mu.m or less in diameter is used. Similarly, the
removal of small protrusions as well as stain is retarded if grinding
stones containing powder detergents exceeding 1,500 .mu.m in grain
diameter are used. It can be understood also that the grain diameter of
the powder synthetic detergent casts no influence on the frictional force.
In removing both the protrusion and the stain from a coated surface, it is
preferred that the protrusion and the stain are removed within the same
duration of time, or the protrusion is removed faster than the stain. It
is not favorable that the stain be removed faster than the protrusion,
because the polishing marks of the protrusion may somewhat remain on the
coated surface. Accordingly, it can be seen from Tables 1 and 2 that a
preferred range of grain diameter for the powder synthetic detergent is
from 30 to 1,500 .mu.m, and that the amount of addition thereof is in the
range of from 0.5 to 20 parts by weight with respect to 100 parts by
weight of the flexible material. By controlling the amount and the grain
size of the detergent within these ranges, the protrusion can be polished
faster than removing the stain. This signifies that the stain is removed
upon completion of the removal of the protrusions, to thereby yield good
operability.
The plastic flexible grinding stone according to the present invention
comprises a flexible material having mixed therewith fine abrasive and
powder synthetic detergent. Accordingly, the flexible grinding stone
according to the present invention is capable of removing small
protrusions and stain from the surface without impairing the flat or
curved plane such as of coated planes by maintaining a uniform surface
against the area to be polished. Furthermore, the grinding stone according
to the present invention facilitates rapid operation because it can be
worked with a small frictional force. The grinding stone according to the
present invention is set as such that the protrusion can be removed more
rapidly than the stain. This not only ameliorates the operability, but
also prevents the surface flatness from being impaired by the reciprocal
movement of the grinding stone after the protrusion is removed.
While the invention has been described in detail and with reference to
specific embodiments thereof, it will be apparent to one skilled in the
art that various changes and modifications can be made therein without
departing from the spirit and scope thereof.
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